Electronic fuses in semiconductor integrated circuits

ABSTRACT

A structure fabrication method. The method includes providing a structure. The structure includes (a) a substrate layer, (b) a first fuse electrode in the substrate layer, and (c) a fuse dielectric layer on the substrate layer and the first fuse electrode. The method further includes (i) forming an opening in the fuse dielectric layer such that the first fuse electrode is exposed to a surrounding ambient through the opening, (ii) forming a fuse region on side walls and bottom walls of the opening such that the fuse region is electrically coupled to the first fuse electrode, and (iii) after said forming the fuse region, filling the opening with a dielectric material.

FIELD OF THE INVENTION

The present invention relates generally to electronic fuses (efuses) and more particularly to diffusion barrier layers serving as efuses.

BACKGROUND OF THE INVENTION

In a conventional semiconductor integrated circuit (chip), there are efuses that can be programmed so as to determine the mode of operation of the chip. Therefore, there is a need for an efuse structure (and a method for forming the same) that is better than the efuses of the prior art.

SUMMARY OF THE INVENTION

The present invention provides an electrical fuse fabrication method, comprising forming a first electrode in a substrate; forming a dielectric layer on top of said first electrode; forming an opening in said dielectric layer such that said first electrode is exposed to a surrounding ambient through said opening; forming a fuse element on side walls and bottom walls of said opening such that said first electrode and said fuse element are electrically coupled together; and filling said opening with a dielectric material.

The present invention provides an efuse structure that is better than the efuses of the prior art.

BRIEF DESCRIPTION OF THE DRAWINGS

FIGS. 1A-1M show cross-section views used to illustrate a fabrication process for forming a semiconductor structure, in accordance with embodiments of the present invention.

FIGS. 2A-2C show cross-section views used to illustrate a fabrication process for forming another semiconductor structure, in accordance with embodiments of the present invention.

FIGS. 3A-3H show cross-section views used to illustrate a fabrication process for forming an alternative semiconductor structure, in accordance with embodiments of the present invention.

DETAILED DESCRIPTION OF THE INVENTION

FIGS. 1A-1M show cross-section views used to illustrate a fabrication process for forming a semiconductor structure 100, in accordance with embodiments of the present invention. More specifically, with reference to FIG. 1A, the fabrication process for forming the semiconductor structure 100 starts with a dielectric layer 110 on top of a front-end-of-line layer (not shown). The front-end-of-line (FEOL) layer contains semiconductor devices such as transistors, resistors, capacitors, etc. (not shown). The dielectric layer 110 comprises a dielectric material such as SiCOH or SiLK on top of the FEOL layer. The dielectric layer 110 can be referred to as an inter-level dielectric layer 110 of a back-end-of-line layer (not shown). Both the dielectric layer 110 and the front-end-of-line layer can comprise oxide, diamond, glass, ceramic, quartz, or polymer.

Next, with reference to FIG. 1B, in one embodiment, trenches 111 a and 111 b are formed in the dielectric layer 110. The trenches 111 a and 111 b can be formed by lithographic and etching processes. The trench 111 a is later used for forming a M1 metal line (not shown), whereas the trench 111 b is later used for forming a first electrode of an efuse structure (not shown).

Next, with reference to FIG. 1C, in one embodiment, a diffusion barrier layer 112 is formed on top of the dielectric layer 110 (including on the bottom walls and the side walls of the trenches 111 a and 111 b). The diffusion barrier layer 112 comprises a diffusion barrier material such as Ta, Ti, Ru, RuTa, TaN, TiN, RuN, RuTaN, a noble metal, or a nitride material of the noble metal. The diffusion barrier layer 112 can be formed by CVD (Chemical Vapor Deposition), PVD (Physical Vapor Deposition), or ALD (Atomic Layer Deposition).

Next, in one embodiment, an electrically conductive layer 114 is formed on top of the diffusion barrier layer 112 resulting in the trenches 111 a and 111 b being filled. The electrically conductive layer 114 comprises an electrically conductive material such as Cu or Al. The electrically conductive layer 114 can be formed by an electroplating process.

Next, in one embodiment, portions of the electrically conductive layer 114 outside the trenches 111 a and 111 b are removed. More specifically, these portions of the electrically conductive layer 114 can be removed by a CMP (Chemical Mechanical Polishing) process performed on the top surface 114′ of the electrically conductive layer 114 until the top surface 110′ the dielectric layer 110 is exposed to the surrounding ambient resulting in the semiconductor structure 100 of FIG. 1C′. The portions of the diffusion barrier layer 112 in the trenches 111 a and 111 b can be referred to as diffusion barrier regions 112 a and 112 b, respectively, as shown in FIG. 1C′. Similarly, the portions of the electrically conductive layer 114 in the trenches 111 a and 111 b can be referred to as a M1 metal line 114 a and a first electrode 114 b of the efuse structure, respectively, as shown in FIG. 1C′.

Next, with reference to FIG. 1D, in one embodiment, an electrically insulating cap layer 120 is formed on top of the semiconductor structure 100 of FIG. 1C′. The electrically insulating cap layer 120 can be formed by CVD of a dielectric material such as Si₃N₄, SiC, SiC(N,H) or SiO₂ on top of the semiconductor structure 100 of FIG. 1C′.

Next, in one embodiment, a dielectric layer 130 is formed on top of the electrically insulating cap layer 120. The dielectric layer 130 comprises a dielectric material such as SiCOH or SiLK. The thickness of the dielectric layer 130 is in the range from 500 angstroms to 10,000 angstroms. The dielectric layer 130 can be formed by CVD or spin-on process.

Next, with reference to FIG. 1E, in one embodiment, via holes 131 a and 131 b and trenches 133 a and 133 b are formed in the dielectric layer 130 and the electrically insulating cap layer 120. More specifically, the via holes 131 a and 131 b and trenches 133 a and 133 b can be formed by a conventional dual damascene process. The via hole 131 a and the trench 133 a are later used for forming a via and a M2 metal line (not shown), respectively, whereas the via hole 131 b and the trench 133 b are later used for forming an efuse (not shown) of the efuse structure.

Next, with reference to FIG. 1F, in one embodiment, a diffusion barrier layer 132 is formed on exposed surfaces of the semiconductor structure 100 of FIG. 1E. The diffusion barrier layer 132 can be formed by CVD, PVD, or ALD of a diffusion barrier material such as Ta, Ti, Ru, RuTa, TaN, TiN, RuN, or RuTaN on exposed surfaces of the semiconductor structure 100 of FIG. 1E.

Next, with reference to FIG. 1G, in one embodiment, electrically conductive regions 134 a and 134 b are formed in the via holes 131 a and 131 b and the trenches 133 a and 133 b. More specifically, the electrically conductive regions 134 a and 134 b can be formed by (i) depositing an electrically conductive material such as Cu or Al on top of the semiconductor structure 100 of FIG. 1F including inside the via holes 131 a and 131 b and the trenches 133 a and 133 b and then (ii) removing the excessive electrically conductive material and portions of the diffusion barrier layer 132 outside the via holes 131 a and 131 b and the trenches 133 a and 133 b resulting in the semiconductor structure 100 of FIG. 1G. The step (i) can be an electroplating process, whereas the step (ii) can be a CMP process.

With reference to FIG. 1G, it should be noted that the diffusion barrier regions 132 a and 132 b are what remain of the diffusion barrier layer 132 (FIG. 1F). The diffusion barrier regions 132 b will serve as an efuse 132 b (also called the fuse element 132 b) of the subsequently formed efuse structure.

Next, with reference to FIG. 1H, in one embodiment, an electrically insulating cap region 140 is formed on top of the electrically conductive region 134 a and the diffusion barrier region 132 a of the semiconductor structure 100 of FIG. 1G such that the electrically conductive region 134 b remains exposed to the surrounding ambient. The electrically insulating cap region 140 can be formed by CVD of a dielectric material such as Si₃N₄, SiC, SiC(N,H) or SiO₂ on top of the semiconductor structure 100 of FIG. 1G followed by lithographic and etching processes.

Next, in one embodiment, the electrically conductive region 134 b is removed resulting in the semiconductor structure 100 of FIG. 1I. More specifically, the electrically conductive region 134 b can be removed by using wet etching.

Next, with reference to FIG. 1J, in one embodiment, a dielectric layer 150 is formed on top of the semiconductor structure 100 of FIG. 1I. The dielectric layer 150 comprises a dielectric material such as SiCOH or SiLK. The dielectric layer 150 can be formed by (i) spin-on or (ii) CVD followed by a CMP process.

Next, with reference to FIG. 1K, in one embodiment, via holes 151 a and 151 b are formed in the dielectric layer 150. The via holes 151 a and 151 b can be formed by lithographic and etching processes. Next, the via hole 151 a is extended down through the electrically insulating cap region 140 by using RIE (Reactive Ion Etching) resulting in a via hole 151 a′ of FIG. 1L.

Next, with reference to FIG. 1M, in one embodiment, diffusion barrier regions 152 a and 152 b are formed on the side walls and bottom walls of the via holes 151 a′ and 151 b. The diffusion barrier regions 152 a and 152 b comprise a diffusion barrier material such as Ta, Ti, Ru, RuTa, TaN, TiN, RuN, RuTaN, a noble metal, or a nitride material of the noble metal. The formation of the diffusion barrier regions 152 a and 152 b is similar to the formation of the diffusion barrier region 112 a and 112 b.

Next, in one embodiment, electrically conductive regions 154 a and 154 b are formed in the via holes 151 a′ and 151 b, respectively. The electrically conductive regions 154 a and 154 b comprise an electrically conductive material such as Cu or Al. The formation of the electrically conductive regions 154 a and 154 b is similar to the formation of the electrically conductive regions 114 a and 114 b described earlier. The electrically conductive region 154 b will serve as a second electrode 154 b of the efuse structure. It should be noted that the first electrode 114 b, the efuse 132 b, and the second electrode 154 b constitute an efuse structure 114 b+132 b+154 b.

In one embodiment, the efuse structure 114 b+132 b+154 b can be programmed by blowing off the efuse 132 b such that the first electrode 114 b and the second electrode 154 b are electrically disconnected from each other. More specifically, the efuse 132 b can be blown off by sending a sufficiently large current through the efuse 132 b.

FIGS. 2A-2C show cross-section views used to illustrate a fabrication process for forming a semiconductor structure 200, in accordance with embodiments of the present invention. More specifically, the fabrication process for forming the semiconductor structure 200 starts with the semiconductor structure 200 of FIG. 2A, wherein the semiconductor structure 200 of FIG. 2A is similar to the semiconductor structure 100 of FIG. 1H. The formation of the semiconductor structure 200 of FIG. 2A is similar to the formation of the semiconductor structure 100 of FIG. 1H.

Next, in one embodiment, a top portion 134 b′ of the electrically conductive region 134 b is removed resulting in an electrically conductive region 234 b being left in the via hole 131 b as shown in FIG. 2A′. The electrically conductive region 134 b can be removed by wet etching. In one embodiment, the removal of the top portion 134 b′ is controlled such that a resistance of the resulting combination of the diffusion barrier regions 132 b and the electrically conductive region 234 b is equal to a pre-specified value.

Next, with reference to FIG. 2B, in one embodiment, a dielectric layer 250 is formed on top of the semiconductor structure 200 of FIG. 2A′. The dielectric layer 250 comprises a dielectric material such as SiCOH or SiLK. The dielectric layer 250 can be formed by (i) spin-on or (ii) CVD followed by a CMP process.

Next, with reference to FIG. 2C, in one embodiment, diffusion barrier regions 252 a and 252 b and electrically conductive regions 254 a and 254 b are formed in the dielectric layer 250 in a manner which is similar to the manner in which the diffusion barrier regions 152 a and 152 b and the electrically conductive regions 154 a and 154 b are formed in FIG. 1M. The electrically conductive region 254 b will serve as a second electrode 254 b of an efuse structure of the semiconductor structure 200 of FIG. 2C. It should be noted that the first electrode 114 b, the efuse 132 b, the electrically conductive region 234 b, and the second electrode 254 b are parts of an efuse structure 114 b+132 b+234 b+254 b.

In one embodiment, the efuse structure 114 b+132 b+234 b+254 b can be programmed in a manner which is similar to the manner in which the efuse structure 114 b+132 b+154 b of semiconductor structure 100 of FIG. 1M is programmed. It should be noted that the efuse structure 114 b+132 b+234 b+254 b can be used as a resistor.

FIGS. 3A-3H show cross-section views used to illustrate a fabrication process for forming a semiconductor structure 300, in accordance with embodiments of the present invention. More specifically, the fabrication process for forming the semiconductor structure 300 starts with the semiconductor structure 300 of FIG. 3A, wherein the semiconductor structure 300 of FIG. 3A is similar to the semiconductor structure 100 of FIG. 1F. The formation of the semiconductor structure 300 of FIG. 3A is similar to the formation of the semiconductor structure 300 of FIG. 1F.

Next, with reference to FIG. 3A′, in one embodiment, a dielectric layer 334 is formed on top of the diffusion barrier layer 132 resulting in the via holes 131 a and 131 b and the trenches 133 a and 133 b being filled. The dielectric layer 334 comprises a dielectric material such as SiLK or SiCOH. The dielectric layer 334 can be formed by CVD or spin-on process.

Next, with reference to FIG. 3B, in one embodiment, an electrically insulating cap region 340 is formed on top of the dielectric layer 334 such that (i) the electrically insulating cap region 340 does not overlap the via hole 131 a and the trench 133 a and (ii) the via hole 131 b and the trench 133 b are directly beneath the electrically insulating cap region 340. The electrically insulating cap region 340 can be formed by CVD or spin-on process of a dielectric material such as Si₃N₄, SiC, SiC(N,H) or SiO₂ on top of the semiconductor structure 300 of FIG. 3A′ followed by lithographic and etching processes.

Next, in one embodiment, the electrically insulating cap region 340 is used as a blocking mask to etch down the dielectric layer 334 until portions of the dielectric layer 334 inside the via hole 131 a and the trench 133 a are completely removed resulting in the semiconductor structure 300 of FIG. 3C. The step of etching down the dielectric layer 334 can be performed by using RIE.

Next, with reference to FIG. 3D, in one embodiment, a diffusion barrier layer 350 is formed on exposed surfaces of the semiconductor structure 300 of FIG. 3C. The diffusion barrier layer 350 can be formed by CVD, PVD, or ALD of a diffusion barrier material such as TaN or TiN on exposed surfaces of the semiconductor structure 300 of FIG. 3C.

Next, with reference to FIG. 3E, in one embodiment, an electrically conductive layer 360 is formed on top of the semiconductor structure 300 of FIG. 3D resulting in the via hole 131 a and the trench 133 a are filled. The electrically conductive layer 360 comprises an electrically conductive material such as Cu or Al. The electrically conductive layer 360 can be formed by an electroplating process.

Next, in one embodiment, (i) portions of the electrically conductive layer 360 and the diffusion barrier layer 350 outside the via hole 131 a and trench 133 a, (ii) portions of the dielectric layer 334 outside the via hole 131 b and the trench 133 b, and (iii) the electrically insulating cap region 340 are removed resulting in the semiconductor structure 300 of FIG. 3F. These removals can be performed by a CMP process.

Next, with reference to FIG. 3G, in one embodiment, an electrically insulating cap layer 370 is formed on top of the semiconductor structure 300 of FIG. 3F. The electrically insulating cap layer 370 comprises a dielectric material such as Si₃N₄, SiC, SiC(N,H) or SiO₂. The electrically insulating cap layer 370 can be formed by CVD or spin-on process.

Next, in one embodiment, a dielectric layer 380 is formed on top of the electrically insulating cap layer 370. The dielectric layer 380 comprises a dielectric material such as SiCOH or SiLK. The dielectric layer 380 can be formed by CVD or spin-on process.

Next, with reference to FIG. 3H, in one embodiment, diffusion barrier regions 382 a and 382 b and the electrically conductive regions 384 a and 384 b are formed in the dielectric layer 380 in a manner which is similar to the manner in which the diffusion barrier regions 152 a and 152 b and electrically conductive regions 154 a and 154 b are formed in FIG. 1M. The electrically conductive region 384 b will serve as a second electrode 384 b of an efuse structure of the semiconductor structure 300 of FIG. 3H. It should be noted that the first electrode 114 b, the efuse 132 b, and the second electrode 384 b constitute an efuse structure 114 b+132 b+384 b.

In one embodiment, the structure of the semiconductor structure 300 of FIG. 3H is similar to the structure of the semiconductor structure 100 of FIG. 1M except that the semiconductor structure 300 comprises the diffusion barrier region 350 a. The diffusion barrier regions 132 a and 350 a can be collectively referred to as a diffusion barrier region 132 a+350 a. The thickness of the diffusion barrier region 132 a+350 a can be customized to a desired thickness by adjusting the thickness of the diffusion barrier region 350 a. As a result, in comparison with the diffusion barrier region 132 b of FIG. 1M, the diffusion barrier region 132 a+350 a of FIG. 3H improves the prevention of diffusion of the electrically conductive material of the electrically conductive region 360 a through the diffusion barrier region 132 a+350 a. In one embodiment, the efuse structure 114 b+132 b+384 b can be programmed in a manner which is similar to the manner in which the efuse structure 114 b+132 b+154 b of semiconductor structure 100 of FIG. 1M is programmed.

In summary, with reference to FIG. 1M, the diffusion barrier regions 132 a and 132 b (i) are similar and (ii) can be formed simultaneously, wherein the diffusion barrier region 132 b can be used as an efuse of the efuse structure 114 b+132 b+154 b. In FIG. 2C, the electrically conductive region 234 b is left in the via hole 131 b so as to decrease the resistance of the efuse. As a result, the resistance of the efuse can be tuned to a desired value. Therefore, the efuse structure 114 b+132 b+234 b+254 b can also be used as a resistor having a desired resistance. In FIG. 3H, the electrically conductive region 360 a is surrounded by the diffusion barrier region 132 a+350 a whose thickness can be at any desirable value.

In the embodiments described above, the dielectric layer 110 is the first inter-level dielectric layer. In an alternative embodiment, the dielectric layer 110 can be second, third, or any inter-level dielectric layer of the back-end-of-line layer.

While particular embodiments of the present invention have been described herein for purposes of illustration, many modifications and changes will become apparent to those skilled in the art. Accordingly, the appended claims are intended to encompass all such modifications and changes as fall within the true spirit and scope of this invention. 

1. An electrical fuse fabrication method, comprising: forming a first electrode in a substrate; forming a dielectric layer on top of said first electrode; forming an opening in said dielectric layer such that said first electrode is exposed to a surrounding ambient through said opening; forming a fuse element on side walls and bottom walls of said opening such that said first electrode and said fuse element are electrically coupled together; and filling said opening with a dielectric material.
 2. The method of claim 1, wherein the substrate comprises a dielectric material selected from the group consisting of oxide, diamond, glass, ceramic, quartz, and polymer.
 3. The method of claim 1, further comprising, after said filling the opening is performed, exposing the fuse element to the surrounding ambient; then forming a second electrode on top of the fuse element such that the second electrode is electrically coupled to the fuse element.
 4. The method of claim 1, wherein the fuse element comprises a diffusion barrier material which is (i) electrically conductive and (ii) capable of preventing metal from diffusing through said fuse element.
 5. The method of claim 4, wherein said diffusion barrier material comprises a material selected from the group consisting of Ta, Ti, Ru, RuTa, TaN, TiN, RuN, RuTaN, a noble metal material, and a nitride material of the noble metal material.
 6. The method of claim 1, further comprising, before said filling the opening is performed, partially filling said opening with an electrically conductive material.
 7. The method of claim 6, wherein said partially filling said opening comprises: overfilling said opening with said electrically conductive material; and then etching back said overfilled electrically conductive material.
 8. The method of claim 1, wherein said opening comprises (i) a via hole and (ii) a trench on top of said via hole, wherein a first cross-section area of said via hole is smaller than a second cross-section area of said trench, and wherein said first and second cross-section areas are parallel to a top surface of the substrate.
 9. An electrical fuse fabrication method, comprising: forming a first electrically conductive region in a substrate; forming a dielectric layer on the substrate and the first electrically conductive region; forming an opening in the dielectric layer such that the first electrically conductive region is exposed to a surrounding ambient through the opening; forming a first diffusion barrier layer on side walls and bottom walls of the opening such that the first diffusion barrier layer is electrically coupled to the first electrically conductive region; after said forming the first diffusion barrier layer is performed, filling the opening with a dielectric material; completely removing the dielectric material in the opening; and then forming a second diffusion barrier layer on top of and in direct physical contact with the first diffusion barrier layer.
 10. The method of claim 9, wherein the substrate comprises a dielectric material.
 11. The method of claim 9, further comprising, after said forming the second diffusion barrier layer is performed, filling the opening with an electrically conductive material.
 12. The method of claim 11, further comprising, after said filling the opening with the electrically conductive material is performed, forming a second electrically conductive region such that the second electrically conductive region is electrically coupled to the first and second diffusion barrier layers.
 13. The method of claim 9, wherein the first diffusion barrier layer comprises a first diffusion barrier material which is electrically conductive, wherein the second diffusion barrier layer comprises a second diffusion barrier material which is electrically conductive, and wherein the first diffusion barrier material is different from the second diffusion barrier material.
 14. The method of claim 9, wherein the first and second diffusion barrier layers comprise a diffusion barrier material which is (i) electrically conductive and (ii) capable of preventing metal from diffusing through the first and second diffusion barrier layers.
 15. The method of claim 14, wherein the diffusion barrier material comprises a material selected from the group consisting of Ta, Ti, Ru, RuTa, TaN, TiN, RuN, RuTaN, a noble metal material, and a nitride material of the noble metal material.
 16. The method of claim 9, wherein the opening comprises (i) a via hole and (ii) a trench on top of the via hole, wherein a first cross-section area of the via hole is smaller than a second cross-section area of the trench, and wherein the first and second cross-section areas are parallel to a top surface of the substrate.
 17. A structure, comprising: (a) a substrate; (b) a first electrode in the substrate; (c) a dielectric layer on top of the substrate and the first electrode; (d) a fuse element buried in the dielectric layer, wherein the fuse element (i) physically separates, (ii) is in direct physical contact with both, and (iii) is sandwiched between a first region and a second region of the dielectric layer; and (e) a second electrode on top of the fuse element, wherein the first electrode and the second electrode are electrically coupled to each other through the fuse element.
 18. The method of claim 17, wherein the substrate comprises a dielectric material.
 19. The structure of claim 17, wherein the fuse element comprises a diffusion barrier material which is (i) electrically conductive and (ii) capable of preventing copper from diffusing through the fuse element.
 20. The structure of claim 19, wherein the diffusion barrier material comprises a material selected from the group consisting of Ta, Ti, Ru, RuTa, TaN, TiN, RuN, RuTaN, a noble metal material, and a nitride material of the noble metal material. 